Metal-oxide-semiconductor (MOS) based integrated circuits have a reliability that is depends in part on the interface between a semiconductor substrate, usually silicon, and a gate dielectric layer. Electrical defects associated with this interface can arise from the presence of unpaired silicon bonds at the interface. Interfacial trap states associated with these defects can be reduced by annealing the circuit, during fabrication, in a forming gas (10% H2) to permit hydrogen atoms to diffuse to, and passivate, the silicon dangling bonds at the interface.
Hot carriers, however, can degrade the interface by displacing the hydrogen atoms at the interface. This loss of hydrogen can lead to threshold-voltage instability, transconductance degradation, and/or an increase in the subthreshold slope.
Deuterium passivation can be used as a more stable substitute for hydrogen passivation. The heavier deuterium isotope can reduce desorption of the passivating species arising from hot-carrier impact. Deuterium can be introduced by heating the circuit during fabrication in a gas containing deuterium to permit the deuterium to diffuse into the circuit.